The world's largest software company unveiled a range of touchscreen netbooks called “slate computer”, but not a much rumoured tablet computer which was said to pose a serious challenge to Apple’s much-anticipated iSlate device, which is expected to be announced later this month.

Michael Gartenberg, analyst at research house Interpret, said Microsoft's “slate” computers were “too large for the pocket, too small to do work on.

“It’s a ‘twener device not optimised for anything,” he wrote on Twitter.

Mr Ballmer said 2009 had been a year of “unprecedent economic turbulence”, but that he was excited about prospects for the coming year.

“This industry really stayed focused and continued to invest, work hard and bring new technology to the market place we really made an impact on people’s lives around the world,” he said.

“From the largest screen on the wall to the smallest screens in people’s pockets, we are delivering the entertainment people want,” he added.

Mr Ballmer said Microsoft has sold more than 39m of its Xbox games console and collected more than $20bn since the platform’s launch. He said the company’s search engine, Bing, will become the default search engine on all Hewlett Packard PCs.